In the field of semiconductor manufacturing, deposition of materials such as metal films on semiconductor substrates can be carried out by a variety of techniques, including chemical vapor deposition (“CVD”), physical vapor deposition (“PVD”), and atomic layer deposition (“ALD”).
Conventional CVD processes for metal film deposition occurs through the volatilization of metal precursors at high temperatures under vacuum. The selection of metal precursors available for CVD is limited by requirements such as high thermal stability and sufficient volatility of the metal precursors. When a precursor is selected and volatilized during the CVD process, the metal precursor is usually only present in the vapor at low concentrations. This can lead to limited film growth resulting in non-conformal films. Moreover, the high temperature requirements of CVD can significantly impact the thermal budget during wafer processing.
With regard to conventional PVD of metal precursors, PVD is fundamentally limited by the nature of a line-of-sight deposition process that results in non-conformal film growth and inability to deposit material in certain types of high aspect ratio structures. Additional shortcomings of PVD include the significant particle levels that are generated in the PVD process, limited control and lack of homogeneity of the deposited film, and process control issues relating to diffusion of the sputtered material.
Conventional ALD processes for deposition of thin films occurs through exposure of the substrate to alternating cycles of precursors to grow atomically thin films. While the ability to grow films in a carefully controlled manner at the atomic level results in conformal deposition, the high number of cycles required to prepare even very thin films leads to slow film growth. Moreover, repetitive valve cycling can also lead to particle generation and maintenance issues.
Currently, several integrated circuit (“IC”) processes require low cost deposition of conformal thin-films for both front end of line and back end of line applications, including capacitor electrodes, barriers, and interconnects.
Some of the limitations of conventional CVD, PVD, and ALD techniques described above suggest a need in the art for improved methods of depositing metal(s) on semiconductor substrates.